feature: added new Lua API for Nginx core's dynamic resolver (FFI).

lib/ngx/resolver.lua

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+local base = require "resty.core.base"
+local get_request = base.get_request
+local ffi = require "ffi"
+local C = ffi.C
+local ffi_new = ffi.new
+local ffi_str = ffi.string
+local ffi_gc = ffi.gc
+local FFI_OK = base.FFI_OK
+local FFI_ERROR = base.FFI_ERROR
+local FFI_DONE = base.FFI_DONE
+local co_yield = coroutine._yield
+
+local BUF_SIZE = 256
+local get_string_buf = base.get_string_buf
+local get_size_ptr = base.get_size_ptr
+
+base.allows_subsystem("http")
+
+ffi.cdef [[
+typedef intptr_t                         ngx_int_t;
+typedef unsigned char                    u_char;
+typedef struct ngx_http_lua_co_ctx_t    *curcoctx_ptr;
+typedef struct ngx_http_resolver_ctx_t  *rctx_ptr;
+
+typedef struct {
+    ngx_http_request_t              *request;
+    u_char                          *buf;
+    size_t                          *buf_size;
+    curcoctx_ptr                     curr_co_ctx;
+    rctx_ptr                         rctx;
+    ngx_int_t                        rc;
+    unsigned                         ipv4:1;
+    unsigned                         ipv6:1;
+} ngx_http_lua_resolver_ctx_t;
+
+int ngx_http_lua_ffi_resolve(ngx_http_lua_resolver_ctx_t *ctx, const char *hostname);
+
+void ngx_http_lua_ffi_resolver_destroy(ngx_http_lua_resolver_ctx_t *ctx);
+]]
+
+local _M = { version = base.version }
+
+local mt = {
+    __gc = C.ngx_http_lua_ffi_resolver_destroy
+}
+
+local Ctx = ffi.metatype("ngx_http_lua_resolver_ctx_t", mt)
+
+function _M.resolve(hostname, ipv4, ipv6)
+    assert(type(hostname) == "string", "hostname must be string")
+    assert(ipv4 == nil or type(ipv4) == "boolean", "ipv4 must be boolean or nil")
+    assert(ipv6 == nil or type(ipv6) == "boolean", "ipv6 must be boolean or nil")
+
+    local buf = get_string_buf(BUF_SIZE)
+    local buf_size = get_size_ptr()
+    buf_size[0] = BUF_SIZE
+
+    local ctx = Ctx({get_request(), buf, buf_size})
+
+    ctx.ipv4 = ipv4 == nil and 1 or ipv4
+    ctx.ipv6 = ipv6 == nil and 0 or ipv6
+
+    local rc = C.ngx_http_lua_ffi_resolve(ctx, hostname)
+
+    local res, err
+    if (rc == FFI_OK) then
+        res, err = ffi_str(buf, buf_size[0]), nil
+    elseif (rc == FFI_DONE) then
+        res, err = co_yield()
+    elseif (rc == FFI_ERROR) then
+        res, err = nil, ffi_str(buf, buf_size[0])
+    else
+        res, err = nil, "unknown error"
+    end
+
+    C.ngx_http_lua_ffi_resolver_destroy(ffi_gc(ctx, nil))
+
+    if err ~= nil then
+        return res, err
+    end
+
+    return res
+end
+
+return _M

lib/ngx/resolver.md

@@ -0,0 +1,140 @@
+Name
+====
+
+`ngx.resolver` - Lua API for Nginx core's dynamic resolver.
+
+Table of Contents
+=================
+
+* [Name](#name)
+* [Status](#status)
+* [Synopsis](#synopsis)
+* [Methods](#methods)
+    * [resolve](#resolve)
+* [Community](#community)
+    * [English Mailing List](#english-mailing-list)
+    * [Chinese Mailing List](#chinese-mailing-list)
+* [Bugs and Patches](#bugs-and-patches)
+* [Author](#author)
+* [Copyright and License](#copyright-and-license)
+* [See Also](#see-also)
+
+Status
+======
+
+TBD
+
+Synopsis
+========
+
+```nginx
+ http {
+     resolver 8.8.8.8;
+
+     upstream backend {
+         server 0.0.0.0;
+
+         balancer_by_lua_block {
+             local balancer = require 'ngx.balancer'
+
+             local ctx = ngx.ctx
+             local ok, err = balancer.set_current_peer(ctx.peer_addr, ctx.peer_port)
+             if not ok then
+                 ngx.log(ngx.ERR, "failed to set the peer: ", err)
+                 ngx.exit(500)
+             end
+         }
+     }
+
+     server {
+         listen 8080;
+
+         access_by_lua_block {
+             local resolver = require 'ngx.resolver'
+
+             local ctx = ngx.ctx
+             local addr, err = resolver.resolve('google.com', true, false)
+             if addr then
+                 ctx.peer_addr = addr
+                 ctx.peer_port = 80
+             end
+         }
+
+         location / {
+             proxy_pass http://backend;
+         }
+     }
+ }
+```
+
+[Back to TOC](#table-of-contents)
+
+Methods
+=======
+
+resolve
+-----------------
+**syntax:** *address,err = resolver.resolve(hostname, ipv4, ipv6)*
+
+**context:** *rewrite_by_lua*, access_by_lua*, content_by_lua*, ngx.timer.*, ssl_certificate_by_lua*, ssl_session_fetch_by_lua**
+
+Resolve `hostname` into IP address by using Nginx core's dynamic resolver. Returns IP address string. In case of error, `nil` will be returned as well as a string describing the error.
+
+The `ipv4` and `ipv6`argument are boolean flags that controls whether A or AAAA DNS records we are interested in.
+Please, note that resolver has its own configuration option `ipv6=on|off`, which has higher precedence over above flags.
+The 'ipv4' flag has default value `true`.
+
+It is required to configure the [resolver](http://nginx.org/en/docs/http/ngx_http_core_module.html#resolver) directive in the `nginx.conf`.
+
+
+[Back to TOC](#table-of-contents)
+
+Community
+=========
+
+[Back to TOC](#table-of-contents)
+
+English Mailing List
+--------------------
+
+The [openresty-en](https://groups.google.com/group/openresty-en) mailing list is for English speakers.
+
+[Back to TOC](#table-of-contents)
+
+Chinese Mailing List
+--------------------
+
+The [openresty](https://groups.google.com/group/openresty) mailing list is for Chinese speakers.
+
+[Back to TOC](#table-of-contents)
+
+Bugs and Patches
+================
+
+Please report bugs or submit patches by
+
+1. creating a ticket on the [GitHub Issue Tracker](https://github.com/openresty/lua-resty-core/issues),
+1. or posting to the [OpenResty community](#community).
+
+[Back to TOC](#table-of-contents)
+
+Author
+======
+
+TBD
+
+Copyright and License
+=====================
+
+TBD
+
+[Back to TOC](#table-of-contents)
+
+See Also
+========
+* library [lua-resty-core](https://github.com/openresty/lua-resty-core)
+* the ngx_lua module: https://github.com/openresty/lua-nginx-module
+* OpenResty: http://openresty.org
+
+[Back to TOC](#table-of-contents)
+

t/resolver.t

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+# vim:set ft= ts=4 sw=4 et fdm=marker:
+
+use Test::Nginx::Socket::Lua 'no_plan';
+use lib '.';
+use t::TestCore;
+
+$ENV{TEST_NGINX_LUA_PACKAGE_PATH} = "$t::TestCore::lua_package_path";
+
+run_tests();
+
+__DATA__
+
+
+=== TEST 1: use resolver in rewrite_by_lua_block
+--- http_config
+    lua_package_path "$TEST_NGINX_LUA_PACKAGE_PATH";
+--- config
+    resolver 8.8.8.8;
+    rewrite_by_lua "ngx.ctx.addr = require('ngx.resolver').resolve('google.com')";
+    location = /resolve {
+        content_by_lua "ngx.say(ngx.ctx.addr)";
+    }
+--- request
+GET /resolve
+--- response_body_like: ^\d{1,3}.\d{1,3}.\d{1,3}.\d{1,3}$
+
+
+
+=== TEST 2: use resolver in access_by_lua_block
+--- http_config
+    lua_package_path "$TEST_NGINX_LUA_PACKAGE_PATH";
+--- config
+    resolver 8.8.8.8;
+    access_by_lua "ngx.ctx.addr = require('ngx.resolver').resolve('google.com')";
+    location = /resolve {
+        content_by_lua "ngx.say(ngx.ctx.addr)";
+    }
+--- request
+GET /resolve
+--- response_body_like: ^\d{1,3}.\d{1,3}.\d{1,3}.\d{1,3}$
+
+
+
+=== TEST 3: use resolver in content_by_lua_block
+--- http_config
+    lua_package_path "$TEST_NGINX_LUA_PACKAGE_PATH";
+--- config
+    resolver 8.8.8.8;
+    location = /resolve {
+        content_by_lua "ngx.say(require('ngx.resolver').resolve('google.com'))";
+    }
+--- request
+GET /resolve
+--- response_body_like: ^\d{1,3}.\d{1,3}.\d{1,3}.\d{1,3}$
+
+
+
+=== TEST 4: query IPv6 addresses
+--- http_config
+    lua_package_path "$TEST_NGINX_LUA_PACKAGE_PATH";
+--- config
+    resolver 8.8.8.8;
+    location = /resolve {
+        content_by_lua "ngx.say(require('ngx.resolver').resolve('google.com', false, true))";
+    }
+--- request
+GET /resolve
+--- response_body_like: ^[a-fA-F0-9:]+$
+
+
+
+=== TEST 5: pass IPv4 address to resolver
+--- http_config
+    lua_package_path "$TEST_NGINX_LUA_PACKAGE_PATH";
+--- config
+    location = /resolve {
+        content_by_lua "ngx.say(require('ngx.resolver').resolve('192.168.0.1'))";
+    }
+--- request
+GET /resolve
+--- response_body
+192.168.0.1
+
+
+
+=== TEST 6: pass IPv6 address to resolver
+--- http_config
+    lua_package_path "$TEST_NGINX_LUA_PACKAGE_PATH";
+--- config
+    location = /resolve {
+        content_by_lua "ngx.say(require('ngx.resolver').resolve('2a00:1450:4010:c05::66'))";
+    }
+--- request
+GET /resolve
+--- response_body
+2a00:1450:4010:c05::66
+
+
+
+=== TEST 7: pass non-existent domain name to resolver
+--- http_config
+    lua_package_path "$TEST_NGINX_LUA_PACKAGE_PATH";
+--- config
+    resolver 8.8.8.8;
+    resolver_timeout 1s;
+    location = /resolve {
+        content_by_lua "ngx.say(require('ngx.resolver').resolve('fake-name'))";
+    }
+--- request
+GET /resolve
+--- response_body
+nilfake-name could not be resolved (3: Host not found)
+
+
+
+=== TEST 8: check caching in Nginx resolver (2 cache hits)
+--- http_config
+    lua_package_path "$TEST_NGINX_LUA_PACKAGE_PATH";
+--- config
+    resolver 8.8.8.8 valid=30s;
+
+    location = /resolve {
+        content_by_lua_block {
+            local resolver = require 'ngx.resolver'
+            ngx.say(resolver.resolve('google.com'))
+            ngx.say(resolver.resolve('google.com'))
+            ngx.say(resolver.resolve('google.com'))
+        }
+    }
+--- request
+GET /resolve
+--- grep_error_log: resolve cached
+--- grep_error_log_out
+resolve cached
+resolve cached